Testing Toxicity and Antidote Effect of Selenium Nanoparticles with <i>Paramecium caudatum</i>

A simple method for assessment of the toxicity and antidote effect of selenium nanoparticles with Paramecium caudatum is presented. Light microscopy in combination with computerized video tracking is employed for the determination of the survival time of P. caudatum. Up to 800 mg/L, selenium nanoparticles are not acutely toxic. With respect to a potential antidote effect, the lethality of silver nanoparticles, silver nitrate, sodium hydrogen selenite, and sodium selenite to P. caudatum was decreased and survival time was extended upon pre-treatment with selenium nanoparticles. Taken together, these findings suggest that administration of selenium nanoparticles attenuates exposure to toxicants. Selenium nanoparticles could be a good functional additive for food management in animals.

Anesthetic Action of Volatile Anesthetics by Using Paramecium as a Model

Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no validated model to assess the presumed candidate sites of the anesthetics. We undertook this study to test the hypothesis that the single-celled Paramecium could be anesthetized and served as a model organism in the study of anesthetics. We assessed the motion of Paramecium cells with Expert Vision system and the chemoresponse of Paramecium cells with T-maze assays in the presence of four different volatile anesthetics, including isoflurane, sevoflurane, enflurane and ether. Each of those volatiles was dissolved in buffers to give drug concentrations equal to 0.8, 1.0, and 1.2 EC50, respectively, in clinical practice. We could see that after application of volatile anesthetics, the swimming of the Paramecium cells was accelerated and then suppressed, or even stopped eventually, and the index of the chemoresponse of the Paramecium cells （denoted as Iche） was decreased. All of the above impacts were found in a concentration-dependent fashion. The biphasic effects of the clinical concentrations of volatile anesthetics on Paramecium simulated the situation of high species in anesthesia, and the inhibition of the chemoresponse also indicated anesthetized. In conclusion, the findings in our studies suggested that the single-celled Paramecium could be anesthetized with clinical concentrations of volatile anesthetics and therefore be utilized as a model organism to study the mechanisms of volatile anesthetics.

Stage-specific appearance of cytoplasmic microtubules around the surviving nuclei during the third prezygotic division of Paramecium

There are six micronuclear divisions during conjugation of Paramecium caudatum:three prezygotic and three postzygotic divisions.Four haploid nuclei are formed during the first two meiotic prezygotic divisions.Usually only one meiotic product is located in the paroral cone(PC)region at the completion of meiosis,which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus.The remaining three located outside of the PC degenerate.The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya,which undergo three successive divisions(postzygotic divisions).However,little is known about the surviving mechanism of the PC nuclei.In the current study,stage-specific appearance of cytoplasmic microtubules(cMTs)was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei,including the PC nuclei and the two types of prospective pronuclei.This suggested that cMTs were involved in the formation of a physical barrier,whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm,where degeneration of extra-meiotic products occurs,another important nuclear event during the third prezygotic division.

Photobiont Flexibility in <i>Paramecium bursaria</i>: Double and Triple Photobiont Co-Habitation

The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each P. bursaria strain. In most cases, the algal partners are restricted to either Chlorella variabilis or Micractinium reisseri (Chlorellaceae, Trebouxiophyceae). Both species are characterized by particular physiology and atypical group I intron insertions, although they are morphologically indistinguishable from each other or from other Chlorella-related species. Both algae are exclusive species that are viable only within P. bursaria cells, and therefore their symbiotic relationship can be considered persistent. In a few cases, the other algal species have been reported as P. bursaria photobionts. Namely, P. bursaria have occasionally replaced their photobiont partner. This paper introduces some P. bursaria strains that maintain more than one species of algae for a long period. This situation prompts speculations about flexibility of host-photo-biont relationships, how P. bursaria replaced these photobionts, and the infection theory of the group I introns.

Tolerance of ciliated protozoan Paramecium bursaria (Protozoa, Ciliophora) to ammonia and nitrites

The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x–9.51 (R2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h–LC50 value for ammonia was found to be 95.50 mg/L. A linear correla- tion between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equa- tion y=2.86x+0.89 (R2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 value and ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.

绿草履虫(Paramecium bursaria)线粒体形态转化的超微结构研究

利用透射电镜研究了绿草履虫(Paramecium bursaria)线粒体的超微结构。除见到细胞质内分布有正常形态的线粒体之外,还有两种形态上有转化的线粒体。其转化形式有下述两种:一种为直管系统,另一种为膜状结构的粗面内质网。这种转化而成的内质网的管状膜为细长而粗细均匀,直径约为40nm。而细胞质内存在的内质网则形态各异,粗细不等,其直径为21.5—60nm。

Nuclear events during conjugation in the poorly studied model ciliate Paramecium jenningsi

Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes(conjugation and autogamy)that rely on their unique nuclear dimorphism,i.e.,the presence of both a germline micronucleus(MIC)and a somatic macronucleus(MAC)in a single cell.The sexual processes show a high diversity in different ciliates.To better understand the differentiation and evolution of sexual processes in closely related species,we investigated the nuclear events during conjugation in Paramecium jenningsi strain GZ,a poorly studied close relative of the well-known P.aurelia complex.The main results include:(1)the conjugation process takes about 48 h,including three prezygotic divisions(meiosis I,II,and mitosis)and three postzygotic divisions;(2)the MICs are dominated by the“parachute”phase at the prophase of meiosis I;(3)after meiosis II,a variable number of nuclei undergo the third prezygotic division,and the two products near the paroral cone become the genetically identical migratory and stationary pronuclei;(4)the synkaryon divides three times to form the MIC and the MAC anlagen,but only one nuclear product of the first postzygotic division completes the next two divisions;and(5)an extra cell division is required to complete the last step of conjugation,during which two MIC anlagen undergo mitotic division while two MAC anlagen are distributed between the daughter cells without division.The comparison of the nuclear events during conjugation in representatives of the class Oligohymenophorea reveals that usually there are three prezygotic divisions and a variable number of postzygotic divisions.However,the number of selected and differentiated nuclei after each division differs among species.This study provided a new model ciliate for further investigations of nuclear selection and differentiation as well as nuclear morphology during meiosis.

农药胁迫对草履虫个体生长和种群动态的影响

采用连续培养法探讨了草履虫(Paramecium caudatum)在甲胺磷、2,4-D丁酯和甲氰菊酯3种农药胁迫条件下的个体生长和种群动态,并利用Logistic种群增长模型对种群的增长曲线进行了分析。结果表明:甲胺磷和甲氰菊酯农药胁迫能改变草履虫细胞的大小和形态;不同农药不同浓度处理下,草履虫密度增长曲线均具有“S”型生长特点;农药胁迫下草履虫密度增长曲线符合Logistic模型(R2>0.8),3种农药胁迫下K值明显降低;甲胺磷和甲氰菊酯农药胁迫下种群最大增长率低于2,4-D丁酯胁迫和对照。

三氟氯氰菊酯对草履虫的毒性作用研究

以草履虫为研究对象,探讨三氟氯氰菊酯对草履虫的急性和慢性毒性作用。结果表明:1 h急性毒性试验显示,浓度越大,死亡率越高。1 h急性毒性作用LC50为1.65 mg.L-1,绝对致死剂量为40.00 mg.L-1,最小致死剂量为0.16 mg.L-1。慢性毒性试验显示,种群增长率与三氟氯氰菊酯浓度呈显著的反应-剂量效应和反应-时间效应,在小于绝对致死剂量情况下,一定时间、一定浓度范围内呈现出浓度越大,种群增长率越高的现象。三氟氯氰菊酯对草履虫生殖的促进作用有可能是环境雌激素效应。

Cd^(++)对草履虫种群的毒性作用

通过研究20℃培养条件下Cd++对草履虫(Paramecium caudatum)种群毒性影响,结果表明:Cd++对草履虫的24hLC50为0.3294mg/L,Cd++浓度对草履虫的种群增长率有极显著影响,多重比较结果显示高浓度组(0.25和0.30mg/L)下草履虫的种群增长率显著小于低浓度下(0.05、0.15和0.20mg/L)的值。回归分析结果表明草履虫种群增长率(Y,/d)与Cd++浓度(X,mg/L)之间呈曲线相关。在一定浓度范围内,草履虫种群增长率随Cd++浓度的升高而呈增大,但高的Cd++浓度显著地降低了草履虫的种群增长率;当Cd++浓度为0.1179mg/L时,草履虫种群有最大增长率1.5442/d。各浓度组与对照组之间的t-检验结果表明在较低的Cd++浓度范围内(0.05、0.10和0.15mg/L)草履虫的种群增长率显著大于对照组的值,而Cd++浓度为0.30mg/L时的草履虫种群增长率显著小于对照组的值。

乙氰菊酯对草履虫的毒性

乙氰菊酯是一种新型菊酯类杀虫剂．以甲苯为助溶剂的水溶液，对草履虫的半致死浓度为１６．３ｍｇ／ｌ；以丙酮为助溶剂的水溶液对草履虫的半致死浓度为２４．０ｍＧ／ｌ。建议在实际应用乙氰菊酯农药时以丙酮代替甲苯做助溶剂为好。

毒死蜱农药对草履虫的毒性研究

研究了有机磷农药毒死蜱对草履虫的急慢性毒性作用。结果表明：毒死蜱溶液的不同浓度对草履虫的生长有极显著影响，浓度越高毒性作用越大，毒死蜱对草履虫的1h急性毒性作用LC50为0．04359mg／L，最大无致死浓度为0．0025mg／L，最小全致死浓度为1．29mg／L。回归分析结果显示，草履虫种群增长率和毒死蜱溶液浓度呈线性相关。慢性毒性试验结果显示，毒死蜱浓度在0．005～1．29mg／L范围内，浓度对数越小（即毒死蜱浓度越小）种群增长率越大，说明毒死蜱溶液在一定低浓度范围内可能具有环境内分泌干扰物效应。

运用激光扫描共聚焦显微技术研究大草履虫口胞器与消化胞器

本文利用激光扫描共聚焦显微技术(Laserscanningconfocalmicroscopy,LSCM)对大草履虫(Parameciumcaudatum)口胞器及消化胞器进行了再观察,通过连续断层扫描和三维重建技术,清晰地显示出草履虫口胞器中前庭、口腔、内口膜、四分膜、背咽膜、腹咽膜等结构,它们的位置和形态与前人的工作结果基本一致,并给出口胞器结构的三维立体构象。观察了虫体内的食物泡及其形成过程。看到胞咽在摄食并形成食物泡时其直径变大的现象,表明Allen(1974)有关消化后期食物泡产生的微小泡回到胞咽处与胞咽膜融合的时间应该是在胞咽直径扩大时,此时微小泡参与到胞咽膜上,进而再参与到新食物泡膜的形成过程中,由此完成膜的循环再利用。在样品制备中采用KMnO4替代了免疫荧光技术中传统的固定剂,固定效果很好,清楚地显示了胞咽膜。

铜、锌离子对尾草履虫的急性毒性试验

试验结果表明,随着离子浓度增高,Cu2+、Zn2+对尾草履虫的毒性增大,且呈现出明显的剂量效应关系.回归分析表明,两种离子的概率单位与浓度对数之间存在着极显著的正相关.Cu2+、Zn2+的1 h半致死浓度(LC50)分别为0.32 mg/L 、11.48 mg/L,95%置信区间分别为0.29～0.36 mg/L ,8.98～14.88 mg/L.Cu2+对尾草履虫的毒性大于Zn2+的毒性;尾草履虫对Cu2+浓度变化比Zn2+更为敏感.

两种典型持久性有机污染物对草履虫急性毒性初探(英文)

滴滴涕和苯并芘这两种典型持久性有机污染物在环境中已广泛分布,因此,本研究利用单细胞真核模式生物-草履虫来研究其急性毒性效应,结果发现其毒性效应存在显著的剂量效应关系。DDT和BaP的半数致死浓度分别为126.012mg.L-1和180.167mg.L-1,且这两种污染物的浓度和概率间存在很好的线性关系。不同浓度的DDT和BaP对草履虫进行毒性作用时,草履虫呈现出不同的形态;比较而言,DDT的毒性作用更大。由于草履虫对这两种毒性物质作用的敏感性,因此,草履虫可作为一种敏感指示生物来评估POPs的长期危害。本研究为水污染的减排和生境的保护提供了一种新途径。最后,就这两种典型POPs对草履虫的毒性机理进行了讨论。

印染废水处理过程及排放水对草履虫遗传毒性评价

草履虫作为指示生物评估印染废水处理过程及排放水的毒性效应。急性毒性结果显示,原水、厌氧工段印染废水、好氧工段印染废水对草履虫的半数致死浓度(24h-LC50)分别为54%、41%、98%;遗传毒性结果显示,印染废水原水、经处理的排放水在6.25%、12.25%稀释梯度下对草履虫造成的DNA损伤较对照组呈显著升高(p<0.01),而排放水对草履虫的DNA损伤较原水无显著性差异;草履虫增殖速率结果显示,印染废水排放水50%稀释梯度下对草履虫增殖速率有抑制作用。暴露于印染废水排放水中10%的草履虫其游动行为发生改变。以上结果表明,印染废水在经过处理后,理化指标均达到国家印染废水行业排放标准,但排放水仍对草履虫产生急性毒性,且遗传毒性较原水没有显著降低。水生生物毒性测试能有效补充理化指标评价,为印染废水行业全面达标排放提供依据。

草履虫培养液的选择及浓度和pH值的影响

采用小麦、大米蔗糖、熟鸡蛋黄、稻草、酵母、猪肺等 6种培养液 ,进行草履虫培养、繁殖的对比实验。实验结果表明 ,稻草和熟鸡蛋黄培养液为草履虫的理想培养液。另外 ,对上述 2种理想培养液的不同浓度和稻草培养液的不同 p H值影响草履虫的生长、繁殖进行了实验 ,实验显示 ,影响较为明显。稻草培养液的最适宜浓度为每 10 0 0 m L水中加入 10～ 2 0 g稻草 ;熟鸡蛋黄培养液的最适宜浓度为每 6 0 m L冷开水中加入 0 .1～ 0 .2 g熟鸡蛋黄 ;稻草培养液的最适宜 p H值为 6 .8～ 7.0。

培养液对尾草履虫种群增长和个体形态的影响

目的 探讨培养液对尾草履虫种群增长和个体形态的影响,并筛选合适的尾草履虫培养液。方法 采用稻草、奶粉、酵母、杂粮4种培养液对尾草履虫进行培养。结果 杂粮培养液、稻草培养液和奶粉培养液里的草履虫生长繁殖的较快。结论 奶粉培养液的适宜浓度为0 2%;杂粮培养液的适宜浓度为4%。杂粮培养液培养的尾草履虫长度、宽度都比较大,个体宽短;稻草培养液培养的尾草履虫长度、宽度都比较小,个体细长。不同的培养液适合不同的培养用途。

含小球藻和无小球藻绿草履虫的基因组DNA多态性的研究

以“绿草履虫 -小球藻”共生系统为材料 ,选用 2 0种随机引物对光培养下含小球藻共生体的草履虫和暗培养诱导除去小球藻共生体的草履虫基因组DNA进行遗传多态分析 ,由扩增产物电泳图谱显示 ,用S40 1、S147、S786、S75 9、S86、S15 5、S140等随机引物扩增出 86 6、 1393、 16 37bp等具有相同特征的电泳条带 ;随机引物S174、S75 0、S76 9、S75 5、S10 3等则扩增出 1385、 185 2、 15 79bp等无共生藻草履虫的特有条带。据此推测 ,绿草履虫中的共生小球藻会导致宿主草履虫基因组结构的改变。同时显示小球藻共生体的基因组可能与宿主基因组有某些相似之处。